transactions can be turned off per Migration.

Closes #9483.

There are SQL Queries that can't run inside a transaction. Since
the Migrator used to wrap all Migrations inside a transaction there
was no way to run these queries within a migration.

This patch adds `self.disable_ddl_transaction!` to the migration to
turn transactions off when necessary.

1 files changed, 15 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 97616ffc58..a0ca36788d 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,20 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Make it possible to execute migrations without a transaction even
+    if the database adapter supports DDL transactions.
+    Fixes #9483.
+
+    Example:
+
+        class ChangeEnum < ActiveRecord::Migration
+          self.disable_ddl_transaction!
+          def up
+            execute "ALTER TYPE model_size ADD VALUE 'new_value'"
+          end
+        end
+
+    *Yves Senn*
+
 *   Assigning "0.0" to a nullable numeric column does not make it dirty.
     Fix #9034.